Gayathri J. answered 10/10/12
GMAT Math and Essay Coaching
Hello Rebekah,
Only the coefficients will change in value.
here, just add the coefficients, of the same variable, taking into consideration the sign also.
the coefficients are -1 and +12; when we add those two , we get +11
Let me give you another example.
Simplify (-5x+8y+12x-19y)
we have two variables here x and y
first take the coefficients of x; -5 and +12. Adding them will give you +7
Noy coefficients of y; +8 and -19. Adding them will give you -11
so the resulting expression will be 7x-11y
Hope this helps.